Gene expression profiling of dSur knock-out flies.. Drosophila melanogaster

In order to investigate the functional relevance of SUR2 (the protein encoded by ABCC9 in humans) for sleep duration, we knocked down the expression of its Drosophila homologue (dSur) in the flies’ nervous system (both central and peripheral). Unlike humans, flies are active predominantly around dawn and dusk and show two large sleep episodes during the day and during the night. Knockdown of dSur dramatically reduced night-sleep, particularly during the first half of the dark period, but had little effect on the flies’ day-sleep. This was true for both elavgal4 UAS-Sur RNAi genotypes compared with their parental control strains. These differences in sleep duration were not due to changes in the circadian clock, as the period of the free-running locomotor activity rhythm in constant darkness was indistinguishable between knockdown flies and controls. Furthermore, no systematic differences in activity levels were found between experimental genotypes and control. Thus, the major effect of knocking down the ABCC9 homologue in flies is shortening nighttime sleep due to a delay of its onset by 3 h. Overall design: To elucidate the functional role of dSur we performed the gene expression profiling of elavgal4 UAS-Sur RNAi genotype compared with their parental control strain (wt) in two time points: Day and Night. The time point Day corresponds to pooled samples every three hours over a 24h period, instead the time point Night corresponds to a single ZT (three hours in the dark phase: ZT15). We used the Drosophila 1.0 custom platform (Agilent Technologies). Total RNA was obtained from the head of 30 flies for each genotype. Four biological replicates were analyzed for dSur-/- and control (wt) samples respectively for the two time points. In total we carried out 16 microarray experiments.